SMSC LAN91C111 - Manual (Page 87)

10/100 Non-PCI Ethernet Single Chip MAC + PHY
Datasheet
SMSC LAN91C111 REV C 87 Revision 1.91 (08-18-08)
DATASHEET
10.4 Typical Flow of Event For Receive
7 The MAC generates a TXEMPTY interrupt upon a
completion of a sequence of enqueued packets.
If a TX failure occurs on any packets, TX INT is
generated and TXENA is cleared, transmission
sequence stops. The packet number of the failure
packet is presented at the TX FIFO PORTS Register.
8 SERVICE INTERRUPT – Read Interrupt Status
Register, exit the interrupt service routine.
Option 1) Release the packet.
Option 2) Check the transmit status in the EPH
STATUS Register, write the packet number of the
current packet to the Packet Number Register, re-
enable TXENA, then go to step 4 to start the TX
sequence again.
S/W DRIVER MAC SIDE
1 ENABLE RECEPTION - By setting the RXEN bit.
2 A packet is received with matching address. Memory
is requested from MMU. A packet number is
assigned to it. Additional memory is requested if
more pages are needed.
3 The internal DMA logic generates sequential
addresses and writes the receive words into memory.
The MMU does the sequential to physical address
translation. If overrun, packet is dropped and
memory is released.
4 When the end of packet is detected, the status word
is placed at the beginning of the receive packet in
memory. Byte count is placed at the second word. If
the CRC checks correctly the packet number is
written into the RX FIFO. The RX FIFO, being not
empty, causes RCV INT (interrupt) to be set. The
RCV_BAD bit of the Bank 1 Control Register controls
whether or not to generate interrupts when bad CRC
packets are received.
5 SERVICE INTERRUPT - Read the Interrupt Status
Register and determine if RCV INT is set. The next
receive packet is at receive area. (Its packet number
can be read from the FIFO Ports Register). The
software driver can process the packet by accessing
the RX area, and can move it out to system memory
if desired. When processing is complete the CPU
issues the REMOVE AND RELEASE FROM TOP OF
RX command to have the MMU free up the used
memory and packet number.
S/W DRIVER MAC SIDE